NVIDIA's nForce4 Ultra chipset

THE RACE TO DELIVER a core logic chipset with PCI Express support for the Athlon 64 has occupied much of our attention over the past few months. We first got a brief hands-on look at VIA's K8T890 chipset, and then we did a full review of ATI's Radeon Xpress 200. In between the two, NVIDIA announced its nForce4 lineup but wasn't able to produce review hardwareuntil now. We've finally gotten our hands on an nForce4 reference motherboard from NVIDIA, and we've subjected it to a grueling battery of tests to see how it performs against the competition from VIA, ATI, and even Intel.

The nForce4 packs a number of innovative new features, including the aforementioned PCI Express capability, a firewall-fortified Gigabit Ethernet controller with hardware acceleration, and a robust implementation of the latest Serial ATA spec, including Native Command Queuing for SCSI-like disk I/O performance under heavy loads. The question is, do all of the marketers' talking points add up to superior performance? We've tested these features, including ActiveArmour and SATA command queuing, and we have some answers. Read on to see what we found.

NVIDIA's special sauce The folks at NVIDIA have obviously worked hard to position the nForce4 chipset family as a distinctive option in the copycat world of core logic chipsets. That's no simple goal to reach in a field where all of the products generally have to conform to the same basic set of standards at any given time. Some of the nForce4's key features are simply shared with the competition, but others are worthy of note because they're unique. Let's have a look at the highlights.

A single-chip design  Like the nForce3, the nForce4 is a single piece of silicon rather than a "chipset" proper with separate north and south bridge chips. Because the Athlon 64 (and AMD's other K8-class processors, including the Opteron and some Semprons) has its own memory controller onboard, the single-chip approach works here. All of NVIDIA's competitors have opted for two-chip configurations that will allow them to swap in new north or south bridge chips independently. The nForce4's single-chip design should virtually eliminate any bottlenecks in chip-to-chip communication between the traditional north and south bridge function blocks.

A block diagram of the nForce4. Source: NVIDIA.

PCI Express  We've already covered the basics of PCI Express in our review of the world's first PCI Express chipsets, the Intel 915G and 925X Express. The nForce4 packs 20 lanes of PCI Express connectivity, sixteen of which will be dedicated to graphics, leaving four lanes for use with PCI-E expansion slots or peripheral chips on the motherboard.

SLI support  The most exciting application for the nForce4's PCI Express lanes is probably NVIDIA's SLI GPU teaming technology. I've listed this capability as a separate bullet point because I'm being generous. Truth is, SLI relies on PCI Express in order to work properly, and any decent PCI-E chipset ought to be able to handle SLI. However, NVIDIA claims the nForce4 is specially optimized for SLI. Whatever the technical merits of that claim, it is true that the first Athlon 64 motherboards with dual graphics slots will definitely be based on the nForce4 chipset. NVIDIA has worked with motherboard manufacturers to make SLI mobos happen, even pioneering a trick PCI-E connector card that will redirect PCI-E lanes as needed. (In a single-card config, 16 lanes go to a single PCI-E X16 slot. In a dual-card config, eight lanes go to each of two physical PCI-E X16 slots.) We'll have more to say about SLI in a separate article shortly.

Advanced storage options  In terms of feature set, the nForce4's storage options are the class of the industry, rivaled only by Intel's. NVIDIA's design team has endowed the nForce4 with four Serial ATA ports and two channels of ATA/133 storage connectivity, for total of eight possible connected devices.

The SATA ports support the latest enhancements from the SATA II spec, including hot-swappable devices, transfer rates up to 300MB/s, and Native Command Queuing. Hard drives with support for 300MB/s transfer rates are still rare birds, but Native Command Queuing (NCQ) is becoming more common. NCQ replicates the sort of smart algorithms that have long been built into SCSI disk controllers on high-end server and workstation computers. By taking in multiple disk I/O requests and intelligently reordering their execution, a NCQ-enabled controller should be able to minimize the mechanical delays in a hard drive mechanismthings like head seeks and rotational latencies that can take milliseconds, a virtual eternity in computer time.

NCQ in action. Source: NVIDIA

The nForce4 should be the first Athlon 64 chipset to market with NCQ suppport; ATI's Radeon Xpress doesn't have it, and VIA's K8T890 north bridge will likely have to wait for a new south bridge chip, in second-gen K8T890 motherboards, in order to gain that capability.

Robust RAID  All eight of the devices plugged connected to the nForce4's storage controllers can participate in RAID arrays of various flavors, including RAID levels 0, 1, 0+1 and the ever-casual "just a bunch of disks." NVIDIA's RAID implementation is unique among Athlon 64 chipsets in its ability to span multiple disk controllers and disk types, so that an ATA/133 drive could be paired up in an array with a comparable SATA drive. Also, the slick NVRAID Windows utility allows users to perform a number of management tasks, including assigning hot-spare drives and viewing a graphical representation of the SATA port on the motherboard where a failed drive is connected. Most impressive, perhaps, is a feature NVIDIA calls RAID morphing; the nForce4 can convert one RAID array type to another on the fly (from RAID 0, say, to RAID 1) without the loss of data on the volume.